This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Despite a reduced incidence of HIV dementia in patients on highly active antiretroviral therapy (HAART), the improved survival has resulted in increased cumulative prevalence of nervous system complications of AIDS. Many fundamental gaps remain in knowledge relating to mechanisms and pathways involved in the development of HIV-associated neurologic disease. The pathogenesis of the disease is unknown, but it is thought to be associated with alterations in the BBB. The focus of this proposal is on how and when disruption of the blood-brain barrier (BBB) occurs. Understanding how and when this occurs could have profound impact on elucidating the pathogenesis of neuroAIDS. In this project we are examining the roles of tight junction proteins, starting with zo-1, and the intracellular mechanisms that lead to the disruption of tight junctions. We have initially focused on focal adhesion kinase (FAK), which is activated in cerebral endothelial cells following exposure to the HIV protein Tat. When localized to sites of integrin clustering, FAK initiates downstream signaling via a phosphorylated tyrosine residue. We are attempting to determine how these intracellular proteins responsible for the disruption of the BBB are regulated in the neuropathogenesis of AIDS. We propose that activation of FAK and the resultant disruption will facilitate entry of cell-associated and cell-free virus into the CNS compartment through the BBB leading to neurological complications. Our primary hypothesis is that activation of focal adhesion kinase (FAK) is a key regulatory event in disruption of tight junction proteins during SIV neuropathogenesis. To test this hypothesis we proposed the following specific aims: Specific Aim 1: Determine if phosphorylation of FAK is a requirement for BBB breakdown and development of encephalitis. This Aim will be tested using in vivo, ex vivo and in vitro approaches. To increase the incidence of encephalitis, and to accelerate progression to terminal disease, we will deplete macaques of CD8 cells prior to infection. Specific Aim 2: Determine if a productively-infected monocyte/macrophage crossing the BBB induces activation of FAK and disruption of tight junctions. These studies will utilize our in vitro 3D model of the BBB. We will utilize specific inhibitors of FAK that are safe for in vivo use, with a goal of extending the study to examine if FAK inhibitors can inhibit the development of encephalitis.